The mailfloss Google Sheets™ add-on verifies email addresses directly within Google Sheets™.
Listing updated:August 13, 2025
Works with:
186
Overview
The mailfloss Google Sheets™ add-on allows you to verify your emails directly within Google Sheets™. Simply connect your mailfloss API key, select your emails, and click the "Verify email addresses" button. A new sheet with the verification results will appear.

The mailfloss Google Sheets™ extension is a super convenient way to do email verification without leaving your Google Sheets™ workflow.

# How to use the mailfloss Google Sheets™ add-on:

Step 1. Installing the extension
Go to Google Marketplace, and search for the extension name "mailfloss email verifier". Click on "Install", this will install the extension directly into your Google Sheets™.

Step 2. Getting the API key
In order to use the extension, you need your API key. You can get the key from the mailfloss app by going to Account Settings -> API key.

Step 3. Setting up the extension
Once you install the extension and get your API key, you will be able to use the extension. For this, you’ll need to enter and connect the API key.

Login to the Google Sheets™ file where you want to use the extension.
Click on the "Extensions" tab and, at the bottom, you should find the option "mailfloss email verifier".

Click on it, and you will see two options: "Verify emails" and "About". The About option contains information that may be helpful about the extension, and Verify emails is where you should enter to get started. Select that option.

A sidebar will open, where you will find an introduction and instructions for the extension, plus a box where you should enter your API key.

Enter your API key and click on the submit button.

Wait a few seconds for it to connect and, if the API key is correct, you should be in.

Step 4. How to use the extension
Once inside the extension, you will see your credits at the bottom of the sidebar. You will also see a button that says "Verify email addresses". 

Select the email addresses you want to verify from your spreadsheet and click "Verify email addresses". 

A new sheet will be created with the name mailfloss results, where you will find all the verification data of your selected email addresses. 
To verify more email addresses, the steps are the same. Just select the emails you want and click Verify. A new sheet will be created with the verification results.

Step 5. Review your settings
You will notice that there is a tab called "Settings". The extension gives you the option of whether you want to get your results color coded. In case you activate this setting, you will see that in the newly created sheet with the verification data, the column called emails will be colored green or red depending on their validation status. 

Below this option, you will see the button "Change API key". In case you need to, the extension will go back to its initial page where you will have to enter the API key again in order to use the extension.

When you close the extension it will remember your API key, so you don't need to enter it every time you open it. The extension will ask for your API key only the first time you're logging in, and in case you want to change it in the future.
Additional information
PricingFree of charge with paid features
Developer
Non-trader
Privacy policy
Terms of service
Mailfloss Email Verifier for Google Sheets™ will ask for the permissions shown below. Learn more
Mailfloss Email Verifier for Google Sheets™ will need access to your Google account
This will allow Mailfloss Email Verifier for Google Sheets™ to :
See, edit, create, and delete all your Google Sheets spreadsheets
View and manage spreadsheets that this application has been installed in
Display and run third-party web content in prompts and sidebars inside Google applications
Connect to an external service
Allow this application to run when you are not present
See your primary Google Account email address
See your personal info, including any personal info you've made publicly available
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